Brushless motor driving device, driving method for a brushless motor, and brushless motor

ABSTRACT

According to one embodiment, a motor driving device includes an output part that supplies an exciting current to an exciting coil, a position detection part that detects a rotational position of a rotor, and a driving control part that produces a driving signal that is based on a detection signal from the position detection part and supplies it to the output part. The position detection part has first, second, and third detection elements that are integrally integrated together with the driving control part and detect rotational positions of the rotor.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 17/381,159, filed on Jul. 20, 2021, which application is basedupon and claims the benefit of priority to Japanese Patent ApplicationNo. 2021-038557 filed on Mar. 10, 2021, the entire contents of which areincorporated by reference in the present application.

FIELD

Embodiments described herein generally relate to a brushless motordriving device, a driving method for a brushless motor, and a brushlessmotor.

BACKGROUND

A technique of a three-phase brushless motor has conventionally beendisclosed where three sensors that detect a rotational position of arotor are arranged at positions with mutual phase differences of 120degrees as an electrical angle. Three sensors are provided separately,so that the number of components is increased. Furthermore, threesensors are mounted at positions with mutual phase differences of 120degrees, so that a support base with large surface area for mounting thesensors thereon is needed and a cost of a motor is increased.Furthermore, adjustment of arrangement positions of sensors is neededfor each motor and is complicated. On the other hand, in a case whereone sensor is provided, there is a risk of defective activation of amotor. A brushless motor driving device, a driving method for abrushless motor, and a brushless motor are desired that are of highversatility and are also capable of reducing a cost of a motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram that generally illustrates a circuit configurationof a brushless motor driving device according to a first embodiment.

FIG. 2 is a diagram that schematically illustrates an arrangementrelationship between a brushless motor driving device and a rotor.

FIG. 3 is a diagram for explaining a driving method for a brushlessmotor driving device.

FIG. 4 is a diagram for explaining a production method for a drivingsignal of a brushless motor driving device at a time of normal rotationof a rotor.

FIG. 5 is a diagram for explaining a production method for a drivingsignal of a brushless motor driving device at a time of reverse rotationof a rotor.

FIG. 6 is a diagram for explaining a signal production method in a casewhere a phase difference is a threshold or less.

FIG. 7 is a diagram for explaining, in detail, a signal productionmethod in a case where a phase difference is a threshold or less.

FIG. 8 is a diagram for explaining a signal production method in a casewhere a phase difference is greater than a threshold.

FIG. 9 is a diagram for explaining, in detail, a signal productionmethod in a case where a phase difference is greater than a threshold.

FIG. 10 is a diagram for explaining an offset of an output signal of anauxiliary sensor and a signal production method thereof.

FIG. 11 is a diagram that illustrates a flow of one embodiment ofcalibration.

FIG. 12 is a diagram that illustrates an example of a plane patternwhere a brushless motor driving device is integrated therein.

FIG. 13 is an exploded perspective view of one embodiment of a motorthat incorporates a brushless motor driving device therein.

DETAILED DESCRIPTION

According to one embodiment, a motor driving device includes an outputpart that supplies an exciting current to an exciting coil thatgenerates a magnetic field that rotates a rotor, a position detectionpart that detects a rotational position of the rotor, and a drivingcontrol part that produces a driving signal that is based on a detectionsignal from the position detection part and supplies it to the outputpart, wherein the position detection part has a first detection elementthat detects a rotational position of the rotor, a second detectionelement that detects a rotational position of the rotor prior to thefirst detection element, and a third detection element that detects arotational position of the rotor subsequent to the first detectionelement, and the first to third detection elements are integrallyintegrated.

Hereinafter, a brushless motor driving device, a driving method for abrushless motor, and a brushless motor according to an embodiment willbe explained in detail with reference to the accompanying drawings.Additionally, the present invention is not limited by these embodiments.

First Embodiment

FIG. 1 is a diagram that generally illustrates a circuit configurationof a brushless motor driving device 100 according to a first embodiment.The brushless motor driving device 100 according to the presentembodiment (that will be called a driving device 100 below) has a sensorpart 10. The sensor part 10 has a main sensor 11, an auxiliary sensor12, and an auxiliary sensor 13. For example, each of the sensors 11, 12,and 13 is composed of a Hall element or is configured as an integratedcircuit that includes an amplifier circuit (non-illustrated) thatamplifies an output signal of a Hall element.

It is possible to provide a Hall element of each of the sensors 11, 12,13 that is composed of silicon or a compound semiconductor such as GaAsor InAs. In a case where a Hall element is composed of silicon, it ispossible to integrate it on a single silicon substrate (non-illustrated)together with other circuit parts that compose the driving device 100.In a case where a Hall element is composed of a compound semiconductor,it is possible to integrate a separate chip (non-illustrated) where aHall element that is composed of a compound semiconductor is formed witha silicon substrate where other circuit parts are formed, by a multichipconfiguration, and integrally integrate them by, for example, a moldresin.

The driving device 100 according to the present embodiment has adetection part 20. The detection part 20 has an offset cancel part 21where an output signal of the main sensor 11 is supplied. It is possibleto provide, for example, the offset cancel part 21 that is configured tosubtract an output signal that is obtained by changing a direction of acurrent that is supplied to a Hall element (non-illustrated) of the mainsensor 11. An output signal of the offset cancel part 21 is supplied toa comparator 22. For example, the comparator 22 has a hysteresischaracteristic and outputs a digital signal where an H level and an Llevel are changed at a zero cross point. The comparator 22 has ahysteresis characteristic, so that it is possible to provide aconfiguration to prevent chattering.

Output signals of the auxiliary sensors 12, 13 are supplied tocomparators 23, 24, respectively. The comparators 23, 24 compare outputsignals of the auxiliary sensors 12, 13 with predetermined thresholdsand output digital signals that are changed to an H level or an L leveldepending on results of comparison thereof. The comparators 23, 24 arecomposed of, for example, window comparators that compare input signalswith two threshold voltages and output digital signals at an H level oran L level depending on results of comparison thereof. A relationshipbetween setting of threshold voltages that are supplied to thecomparators 23, 24 and output signals of the comparators 23, 24 will bedescribed later.

The detection part 20 has an AD converter 25 where an output of theoffset cancel part 21 is supplied, and AD converters 26, 27 where outputsignals of the auxiliary sensors 12, 13 are supplied. The respective ADconverters 25 to 27 convert output signals of the respective sensors 11,12, and 13 into digital signals and output them.

The driving device 100 according to the present embodiment has a controlpart 30. The control part 30 has a signal processing part 31, athreshold voltage production part 32, a phase difference detection part33, a sensor output selection part 34, and a driving signal productionpart 35.

The signal processing part 31 executes a predetermined arithmeticprocess by using an output signal of the respective AD converters 25 to27. For example, the signal processing part 31 executes an arithmeticprocess by using digital signals that are acquired from the respectiveAD converters 25 to 27 and supplies a result of processing thereof tothe threshold voltage production part 32, the phase difference detectionpart 33, and the driving signal production part 35.

The driving device 100 according to the present embodiment has a memorypart 50. The memory part 50 holds results of selection of the auxiliarysensors that are acquired in calibration that is executed at a time ofmotor activation and values of output signals of the auxiliary sensors12, 13. Furthermore, the memory part 50 holds data of a drivingcondition in calibration at a time of activation thereof. The drivingsignal production part 35 produces a driving signal that rotates a rotor62 at a constant frequency (rotational frequency), for example, inresponse to a signal that is supplied at a predetermined timing from thememory part 50 through the signal processing part 31 in calibrationthereof.

The threshold voltage production part 32 analog-converts a digitalsignal that is supplied from the signal processing part 31, producesthreshold voltages of the comparators 23, 24 from output signals of theAD converters 26, 27 that are acquired in calibration that is executedat a time of motor activation, and supplies them to the comparators 23,24. Calibration will be described later.

The phase difference detection part 33 detects phase differences amongoutput signals of the respective sensors 11, 12, 13 that are suppliedfrom the signal processing part 31. An output signal of the phasedifference detection part 33 is supplied to the sensor output selectionpart 34 through the signal processing part 31.

The sensor output selection part 34 selects a signal that is supplied tothe driving signal production part 35, in response to an output signalof the phase difference detection part 33 that is supplied through thesignal processing part 31. In a case where a phase difference between anoutput signal of the main sensor 11 and an output signal of theauxiliary sensor 12 at a time of normal rotation of the rotor 62 is apredetermined threshold or less, the sensor output selection part 34selects output signals from the main sensor 11 and the auxiliary sensor12 and supplies them to the driving signal production part 35. Athreshold is, for example, 30 degrees as an electrical angle. Athreshold and a selection method for an output signal will be describedlater.

The driving signal production part 35 produces a driving signal by usinga signal that is supplied from the sensor output selection part 34 andsupplies it to an output circuit part 40.

The output circuit part 40 has output transistors 41 to 46. Therespective output transistors 41 to 46 have free wheel diodes 411 to 416between sources-drains thereof. The respective output transistors 41 to46 of the output circuit part 40 compose a bridge circuit and execute,for example, 120-degree conduction in response to a driving signal fromthe driving signal production part 35. The respective output transistors41 to 46 supply exciting currents to exciting coils LU, LV, LW of a coilpart 61 of a motor 60 through output lines 301 to 303. The excitingcoils LU, LV, LW are excited by exciting currents so as to generatemagnetic fields. The rotor 62 that is composed of a permanent magnet isrotated depending on magnetic fields that are generated by the excitingcoils LU, LV, LW. Additionally, the exciting coils LU, LV, LW may becomposed of delta connection. The driving device 100 that includes thesensor part 10 is arranged at a position that is close to the rotor 62of the motor 60.

In the driving device 100 according to a first embodiment, the mainsensor 11, the auxiliary sensor 12, and the auxiliary sensor 13 areintegrally integrated. Furthermore, in the driving device 100, resultsof selection of the auxiliary sensors 12, 13 that are acquired at a timeof calibration and values of output signals of the respective auxiliarysensors 12, 13 are held in the memory part 50 and the threshold voltageproduction part 32 sets threshold voltages of the respective comparators23, 24. Therefore, it is possible to change setting values of thresholdvoltages for each motor where the driving device 100 is mounted, so thata configuration with high versatility is provided.

FIG. 2 is a diagram that schematically illustrates an arrangementrelationship between the driving device 100 and the rotor 62. Acomponent that corresponds to that of an embodiment as already describedwill be provided with an identical sign so as to provide a redundantdescription only in a case of need. Hereinafter, the same applies. FIG.2 illustrates an example of a case of an inner rotor. For example, therotor 62 is composed of two poles such as an N pole and an S pole asillustrated in the figure. The driving device 100 where the respectivesensors 11, 12, 13 of the sensor part 10 are integrally integrated isprovided so as to be close to the rotor 62. A center line 600 passesthrough a center of the main sensor 11. A broken line 603 indicates aline that passes through a center of the auxiliary sensor 12 from acenter O of the rotor 62 and a broken line 604 indicates a line thatpasses through a center of the auxiliary sensor 13 from the center O.

Phase differences between an output signal of the main sensor 11 andoutput signals of the respective auxiliary sensors 12, 13 are producedby angles α1, α2 that are produced between the center line 600 and therespective broken lines 603, 604. Preferably, the auxiliary sensors 12,13 are provided at line-symmetric positions relative to the main sensor11, that is, the center line 600 as a center. That is, arrangement isprovided in such a manner that α1 and α2 are equal. The auxiliarysensors 12, 13 are arranged at line-symmetric positions relative to thecenter line 600 as a center, so that it is possible to provide aconfiguration that has a relationship where a phase of an output signalof one of the auxiliary sensors 12, 13 is advanced relative to that ofan output signal of the main sensor 11 and an output signal of the otheris delayed by an identical phase difference.

At a time of normal rotation of the rotor 62 as indicated by an arrow601, the auxiliary sensor 12 outputs an output signal that precedes themain sensor 11 and the auxiliary sensor 13 outputs an output signal thatfollows it. At a time of reverse rotation as indicated by an arrow 602,the auxiliary sensor 13 outputs an output signal that precedes the mainsensor 11 and the auxiliary sensor 12 outputs an output signal thatfollows the main sensor 11. The driving device 100 according to thepresent embodiment detects a rotational position of the rotor 62 byutilizing phase differences between output signals of the main sensor 11and the auxiliary sensors 12, 13. Furthermore, an anteroposteriorrelation between output signals of the main sensor 11 and the auxiliarysensors 12, 13 differs depending on a direction of rotation of the rotor62, so that it is possible to detect a direction of rotation of therotor 62 and it is possible to avoid a risk of defective activation ofthe motor 60. Additionally, rotation of the rotor 62 may be representedas rotation of the motor 60.

Output signals of the respective sensors 11, 12, and 13 are generated inresponse to approaching of an N pole and an S pole of a permanent magnetof the rotor 62 to the respective sensors 11, 12, and 13. That is, amagnitude of an output signal of each of the sensors 11, 12, and 13 doesnot depend on a rotational speed of the rotor 62. Therefore, levels ofoutput signals of the respective auxiliary sensors 12, 13 that areacquired by calibration that is executed at a time of activation thereofare set as threshold voltages of the comparators 23, 24 and outputsignals from the respective auxiliary sensors 12, 13 are compared withthese threshold voltages in the respective comparators 23, 24, so thatit is possible to detect a rotational positon of the rotor 62.

Additionally, in a case of a configuration of an outer rotor, thedriving device 100 is arranged on an inner side of the rotor 62, thatis, on a side of the center O. Similarly to a configuration of an innerrotor, it is possible to provide a configuration that causes therespective sensors 11, 12, 13 to respond to rotation of the rotor 62.

Next, a driving method for the driving device 100 will be explained byusing FIG. 3 . FIG. 3 is a diagram for explaining a driving method for abrushless motor driving device, and a diagram for explaining arelationship among output signals of the respective sensors 11, 12, and13 at a time of normal rotation of the rotor 62. A solid line 501 in atop section indicates an angle of rotation of the rotor 62. In a casewhere the rotor 62 is composed of a permanent magnet with two poles, anangle of rotation of the rotor 62 corresponds to an electrical angle.P18 indicates a timing of an angle of rotation of 180 degrees and P00indicates a timing of an angle of rotation of 360 degrees, therefore, anangle of rotation of 0 degrees.

A subsequent section indicates an output signal 502 of the main sensor11 that is supplied through the offset cancel part 21, as a pseudo-sinewave. For example, the main sensor 11 generates a negative voltage as anN pole of the rotor 62 approaches, or generates a positive voltage as anS pole thereof approaches. The output signal 502 of the main sensor 11is zero at timings of connection of an S pole and an N pole of the rotor62. That is, the output signal 502 of the main sensor 11 is zero attimings P0, P10 that correspond to timings of connection of an S poleand an N pole of the rotor 62. The timings P0, P10 are zero crosspoints.

A subsequent section indicates output signals 503, 504 of the auxiliarysensors 12 and 13, as pseudo-sine waves. Conveniently, indices (12),(13) that indicate the auxiliary sensors 12, 13 that correspond to theoutput signals 503, 504 are additionally provided. For example, theauxiliary sensors 12, 13 generate negative voltages as an N pole of therotor 62 approaches, or generate positive voltages as an S pole thereofapproaches, similarly to the main sensor 11. The output signal 503 ofthe auxiliary sensor 12 is compared with a threshold voltage thA1 and athreshold voltage thA2 in the comparator 23. Depending on results ofcomparison with the threshold voltages thA1, thA2, a timing P1 when aphase is advanced by 120 degrees relative to a timing P18 when theoutput signal 502 of the main sensor 11 is zero, and a timing P2 when aphase is delayed by 60 degrees relative thereto are detected.

Similarly, the output signal 504 of the auxiliary sensor 13 is comparedwith a threshold voltage thB1 and a threshold voltage thB2 in thecomparator 24, and a timing P3 when a phase is advanced by 60 degreesrelative to the timing P18 when the output signal 502 of the main sensor11 is zero and a timing P4 when a phase is delayed by 120 degrees aredetected. For example, the respective threshold voltages thA1, thA2,thB1, thB2 are set based on output levels of output signals of therespective auxiliary sensors 12, 13 at a time of calibration that isexecuted at a time of activation of the motor 60. Calibration will bedescribed later.

A subsequent section indicates a digital signal 505 that is producedfrom the output signal 502 of the main sensor 11. A waveform of theoutput signal 502 of the main sensor 11 that is supplied through theoffset cancel part 21 is shaped by the comparator 22 so as to obtain thedigital signal 505. The digital signal 505 is changed from an L level toan H level at the timing PO when the output signal 502 is changed from anegative voltage to a positive voltage, that is, a zero cross point. Forexample, the comparator 22 has a hysteresis characteristic whereswitching between an H level and an L level is caused at a zero crosspoint of the output signal 502.

A subsequent section indicates a digital signal 506 of the auxiliarysensor 12 that is output by the comparator 23. For example, thecomparator 23 outputs the digital signal 505 at an H level and an Llevel in response to the threshold voltage thA1 on a low side and thethreshold voltage thA2 on a high side.

A subsequent section indicates a digital signal 507 of the auxiliarysensor 13 that is output by the comparator 24. For example, thecomparator 24 outputs a digital signal at an H level and an L level inresponse to the threshold voltage thB1 on a low side and the thresholdvoltage thB2 on a high side.

The threshold voltages thA1, thA2, thB1, thB2 of the respective sensors12, 13 are set in calibration at a time of motor activation. Thethreshold voltages thA1, thA2, thB1, thB2 are set based on output levelsof output signals of the auxiliary sensors 12, 13 at a timing when arelationship is provided in such a manner that respective phasedifferences of electrical angles are 120 degrees, in the output signal502 of the main sensor 11.

The driving signal production part 35 produces driving signals HU, LU,HV, LV, HW, LW that are supplied to the respective output transistors 41to 46, by using the three digital signals 505 to 507. The driving signalHU as indicated by a solid line 610 in a subsequent section is suppliedto the output transistor 41 in an upper section for a U phase and thedriving signal LU as indicated by a solid line 611 in a subsequentsection is supplied to the output transistor 44 in a lower section forthe U phase.

Similarly, the driving signal HV as indicated by a solid line 612 in asubsequent section is supplied to the output transistor 42 on an uppersection for a V phase and the driving signal LV as indicated by a solidline 613 in a subsequent section is supplied to the output transistor 45on a lower section for the V phase. Similarly, the driving signal HW asindicated by a solid line 614 in a subsequent section is supplied to theoutput transistor 43 on an upper section for a W phase and the drivingsignal LW as indicated by a solid line 615 in a subsequent section issupplied to the output transistor 46 on a lower section for the W phase.

The respective output transistors 41 to 46 are driven by the drivingsignals HU, LU, HV, LV, HW, LW, for example, in 120-degree conduction.Additionally, for explanatory convenience, the driving signals HU, HV,HW indicate signals for turning on P-type output transistors 41 to 43,so that indication is provided in such a manner that a logic level ofH/L is inverted.

In the driving device 100 according to the present embodiment, thedriving signals HU, LU, HV, LV, HW, LW are produced based on outputlevels of output signals of the main sensor 11 and the two auxiliarysensors 12, 13 that are integrally integrated. The threshold voltagesthA1, thA2, thB1, thB2 of the comparators 23, 24 are set by outputlevels of output signals of the auxiliary sensors 12, 13 that aredetected at a point of time for a predetermined phase differencerelative to an output signal of the main sensor 11 at a time ofcalibration that is executed at a time of activation of the motor 60.Output signals from the auxiliary sensors 12, 13 are compared withthreshold voltages, so that it is possible to detect a rotationalposition of the rotor 62. Even though the main sensor 11 and theauxiliary sensors 12, 13 are formed integrally, it is possible to detecta rotational position of the rotor 62 similarly to a conventionalthree-phase brushless motor. Furthermore, it is possible to set properthreshold voltages for each motor in calibration, so that it is possibleto provide the driving device 100 with versatility.

Next, one embodiment of a production method for a driving signal that isexecuted by the driving device 100 at a time of normal rotation of therotor 62 will be explained by using FIG. 4 . FIG. 4 is a diagram forexplaining output signals of the respective sensors 11, 12, 13 at a timeof normal rotation of the rotor 62. Production of signals in a topsection to a fifth section is identical to that of FIG. 3 as alreadydescribed. In the present embodiment, a digital signal 2 is produced byusing the digital signal 505 of the main sensor 11 and a digital signal1 of the auxiliary sensor 12.

For example, a period of time T2 is measured that corresponds to a phasedifference of 60 degrees between the timing P18 of rising of the digitalsignal 505 of the main sensor 11 and the timing P2 of falling of thedigital signal 1 of the auxiliary sensor 12. Measurement is executed by,for example, a counter (non-illustrated) that is provided in the signalprocessing part 31. An arithmetic process is executed by using themeasured period of time T2 in the signal processing part 31 so as tocalculate periods of time T3, T1, and T4 to T6 that correspond to phasedifferences of 60 degrees. The digital signal 2 with a phase where thephase is delayed by 120 degrees relative to the digital signal 505 thatis produced depending on the output signal 502 of the main sensor 11 isproduced by using the measured period of time T2 and the calculatedperiods of time T1, T3 to T6. A total value of the periods of time T1 toT6 is one cycle of the digital signal 2. The digital signal 2 isproduced in the driving signal production part 35.

Additionally, although it is also possible to execute an arithmeticprocess by using only the digital signal 505 of the main sensor 11 so asto produce the digital signal 2 with a phase where the phase is delayedby 120 degrees, it is possible to produce the digital signal 2 that ismore accurate, by also using information of the auxiliary sensor 12.Furthermore, it is also possible to estimate the period of time T3 byusing information of a frequency variation in several cycles.

In a signal production method according to the present embodiment, anarithmetic process is executed by using the digital signal 505 of themain sensor 11 and the digital signal 1 of the auxiliary sensor 12 so asto produce the digital signal 2 where an H level and an L level arechanged at a timing of a predetermined phase difference. Specifically,the digital signal 2 as indicated by a solid line 508 is produced wherea phase thereof is delayed by 120 degrees relative to the output signal502 of the main sensor 11. A method that produces a driving signal byusing the main sensor 11, the digital signal 1 of the auxiliary sensor12, and the digital signal 2 is similar to that of an example of FIG. 3and hence is omitted. The driving signals HU, LU, HV, LV, HW, LW areproduced by the driving signal production part 35.

A signal production method where a production method for the digitalsignal 1 and the digital signal 2 differs depending on a phasedifference between the output signal 502 of the main sensor 11 and theoutput signal 503 of the auxiliary sensor 12 will be described later.

FIG. 5 is a diagram for explaining a production method for outputsignals of the respective sensors 11, 12, 13 and a driving signal at atime of reverse rotation of the rotor 62. A top section indicates anangle of rotation of the rotor 62 by a solid line 511. A subsequentsection indicates an output signal 512 of the main sensor 11.

A subsequent section indicates output signals of the auxiliary sensors12, 13 by solid lines 513, 514, respectively. A relationship betweenmagnetic poles of a permanent magnet of the rotor 62 and output voltagesof the respective sensors 11, 12, 13 is identical to that of a case ofnormal rotation of the rotor 62.

A subsequent section indicates, by a solid line 515, a digital signal ofthe main sensor 11 that is output by the comparator 22. Changes to an Hlevel and an L level are caused at timings P0, P10 that are zero crosspoints for the main sensor 11. A subsequent section indicates, by asolid line 516, the digital signal 1 where a phase thereof is advancedby 120 degrees relative to a digital signal 515 of the main sensor 11. Adigital signal 516 is produced from an output signal 514 of theauxiliary sensor 13.

That is, in calibration at a time of motor activation, a level of anoutput signal of the auxiliary sensor 13 at the timing P3 that is apoint of time when a phase thereof is advanced by 120 degrees relativeto an output signal of the main sensor 11 is detected and set as thethreshold voltage thB2. Furthermore, an output level of an output signalat the timing P4 when a phase thereof is delayed by 60 degrees relativeto the output signal 512 of the main sensor 11 is detected and set asthe threshold voltage thB1. The digital signal 1 as indicated by thesolid line 516 is produced by the comparator 24 where the thresholdvoltages thB1, thB2 are set.

In a signal production method according to the present embodiment, thedigital signal 2 as indicated by a solid line 518 is produced by usingthe digital signal 515 of the main sensor 11 and the digital signal 1 ofthe auxiliary sensor 13. For example, a period of time T12 is measuredthat corresponds to a phase difference of 60 degrees between the timingP18 of falling of the digital signal 515 of the main sensor 11 and thetiming P4 of rising of the digital signal 1 of the auxiliary sensor 13.Measurement is executed by, for example, a counter (non-illustrated)that is provided in the signal processing part 31. An arithmetic processis executed in the signal processing part 31 by using the measuredperiod of time T12 so as to calculate period of times T13, T11, and T14to T16 that correspond to phase differences of 60 degrees. The digitalsignal 2 with a phase where the phase is delayed by 120 degrees relativeto the digital signal 515 that is produced depending on the outputsignal 512 of the main sensor 11 is produced by using the measuredperiod of time T12 and the calculated periods of time T11, T13 to T16. Atotal value of the periods of time T11 to T16 is one cycle of thedigital signal 2. The digital signal 2 is produced in the driving signalproduction part 35.

Additionally, although it is also possible to execute an arithmeticprocess by using only the digital signal 515 of the main sensor 11 so asto produce the digital signal 2 with a phase where the phase is delayedby 120 degrees, it is possible to produce the digital signal 2 that ismore accurate, by also using information of the auxiliary sensor 13.

In a signal production method according to the present embodiment, anauxiliary sensor that produces the digital signal 1 depending on adirection of rotation of the rotor 62 is selected and timings when H/Lof the digital signal 1 is switched are timings before output signals ofthe auxiliary sensor reach a peak value and a bottom value, so that itis possible to simplify a circuit configuration for producing thedigital signal 1 from the output signals of the auxiliary sensor.

For example, it is possible to provide the comparator 24 that outputsthe digital signal 516 from the auxiliary sensor 13 and is composed of awindow comparator that compares the output signal 514 of the auxiliarysensor 13 with the two threshold voltages thB1, thB2. A method thatproduces the driving signals HU, LU, HV, LV, HW, LW by using the digitalsignal 515 of the main sensor 11, the digital signal 516 of theauxiliary sensor 13, and a digital signal 518 is similar to that of acase of an embodiment of FIG. 3 and hence is omitted.

A signal production method in a case where a phase difference betweenoutput signals of the main sensor 11 and the auxiliary sensor 12 at atime of normal rotation of the rotor 62 is a threshold or less will beexplained by using FIG. 6 and FIG. 7 . FIG. 7 is a diagram that enlargesand illustrates a top section to a third section of FIG. 6 .

In calibration at a time of activation of the motor 60, a phasedifference between the output signal 502 of the main sensor 11 and theoutput signal 503 of the auxiliary sensor 12 at a time of normalrotation of the rotor 62 is compared with a predetermined threshold.That is, a phase difference θ1 between the output signal 502 of the mainsensor 11 as indicated in second sections of FIG. 6 and FIG. 7 and theoutput signal 503 of the auxiliary sensor 12 as indicated in thirdsections thereof is detected and compared with a threshold. A thresholdis, for example, 30 degrees.

As enlarged and illustrated in FIG. 7 , the phase difference θ1 betweenoutput signals of the main sensor 11 and the auxiliary sensor 12 isdetected by a phase difference between a timing PU when the outputsignal 502 of the main sensor 11 is provided at a peak value and atiming PU12 when the output signal 503 of the auxiliary sensor 12 isprovided at a peak value or a phase difference between a timing PB whenthe output signal 502 of the main sensor 11 is provided at a bottomvalue and a timing PB12 when the output signal 503 of the auxiliarysensor 12 is provided at a bottom value.

The timing PB when the output signal 502 of the main sensor 11 isprovided at a bottom value is present at a position where the timing P18that is advanced by 90 degrees relative to an angle of rotation of themain sensor 11 is 180 degrees. Therefore, in a case where the phasedifference θ1 is 30 degrees or less, the timing P1 of the output signal503 of the auxiliary sensor 12 that is advanced by 120 degrees relativeto the timing P0 when the output signal 502 of the main sensor 11 iszero is present at a predetermined position before reaching the timingPB12 when the output signal 503 of the auxiliary sensor 12 is providedat a bottom value. Similarly, the timing P2 when a phase of the outputsignal 503 of the auxiliary sensor 12 is delayed by 60 degrees relativeto the timing P0 when the output signal 502 of the main sensor 11 iszero is present at a predetermined position before reaching the timingPU12 when the output signal 503 of the auxiliary sensor 12 is providedat a peak value.

Therefore, it is possible to detect rotational positions of the rotor 62at the timing P1 where a phase thereof is advanced by 120 degreesrelative to the timing P18 when an angle of rotation of the main sensor11 is 180 degrees and the timing P2 when a phase thereof is delayed by60 degrees relative thereto, by a configuration where the output signal503 of the auxiliary sensor 12 is compared with the threshold voltagesthA1, thA2 that are set at a time of calibration. For example, it ispossible to provide the comparator 23 that is composed of a windowcomparator that compares the output signal 503 of the auxiliary sensor12 with the two threshold voltages thA1, thA2.

It is possible to produce the digital signal 2 as indicated by the solidline 508 in a bottom section of FIG. 6 as a signal with a phase that isdelayed by 120 degrees where T1 to T6 are produced by using the digitalsignal 505 of the main sensor 11 and the digital signal 1 of theauxiliary sensor 12 similarly to a case of FIG. 4 . A method thatproduces the driving signals HU, LU, HV, LV, HW, LW by using the digitalsignal 505 of the main sensor 11, the digital signal 1 that is producedfrom the output signal 502 of the auxiliary sensor 12, and the digitalsignal 2 is similar to that of an example of FIG. 3 and hence isomitted.

A signal production method in a case where a phase difference between anoutput signal of the main sensor 11 and an output signal of theauxiliary sensor 12 at a time of normal rotation of the rotor 62 isgreater than a threshold will be explained by using FIG. 8 and FIG. 9 .FIG. 9 is a diagram that enlarges and illustrates a top section to athird section of FIG. 8 .

The timing PB when the output signal 502 of the main sensor 11 isprovided at a bottom value is positioned at a timing that is advanced by90 degrees relative to the timing P18 when an angle of rotation of themain sensor 11 is 180 degrees, and the timing PU when it is provided ata peak value is positioned at a timing that is delayed by 90 degreesrelative thereto. Therefore, in a case where a phase difference θ2between the timing PU when the output signal 502 of the main sensor 11is provided at a peak value and a timing PU14 when an output signal 523of the auxiliary sensor 12 is provided at a peak value or between thetiming PB when the output signal 502 of the main sensor 11 is providedat a bottom value and a timing PB14 when that of the auxiliary sensor 12is provided at a bottom value is greater than 30 degrees, a timing P14of an output signal 524 of the auxiliary sensor 13 that is advanced by60 degrees relative to the timing P0 when the output signal 502 of themain sensor 11 is zero is present at a predetermined position beforereaching a timing PB13 when the output signal 524 of the auxiliarysensor 13 is provided at a bottom value. Similarly, a timing P13 when aphase of the output signal 524 of the auxiliary sensor 13 is delayed by120 degrees relative to the timing P0 when the output signal 502 of themain sensor 11 is zero is present at a predetermined position beforereaching a timing PU13 when the output signal 524 of the auxiliarysensor 13 reaches a peak value.

Therefore, in a case where a phase difference is greater than 30degrees, the auxiliary sensor 13 is selected and the output signal 524of the auxiliary sensor 13 is compared with the threshold voltages thB1,thB2 that are set at a time of calibration, so that it is possible todetect rotational positions of the rotor 62 at the timing P14 when aphase thereof is advanced by 60 degrees relative to the timing P18 whenan angle of rotation of the main sensor 11 is 180 degrees and the timingP13 when a phase thereof is delayed by 120 degrees relative thereto. Aconfiguration where a bottom value and a peak value of the output signal524 of the auxiliary sensor 13 are detected does not have to beprovided, so that it is possible to simplify a circuit configuration.For example, it is possible to provide the comparator 24 that obtains adigital signal 526 from the auxiliary sensor 13 and is composed of awindow comparator that compares the output signal 524 of the auxiliarysensor 13 with the two threshold voltages thB1, thB2.

In a case where the phase difference θ2 between output signals of themain sensor 11 and the auxiliary sensor 12 is greater than a thresholdof 30 degrees, the digital signal 1 is produced by using the outputsignal 524 of the auxiliary sensor 13. It is possible to produce thedigital signal 2 as indicated by a solid line 528 as a signal with aphase that is delayed by 120 degrees relative to the digital signal 1 byexecuting an arithmetic process of the digital signal 1. Additionally,similarly to a case of FIG. 4 , the digital signal 2 may be produced bymeasuring a time that corresponds to a phase difference of 60 degreesrelative to the digital signal 1 of the auxiliary sensor 13 by alsousing information of a digital signal 525 of the main sensor 11, andexecuting an arithmetic process by using such a measurement value.

Additionally, as described, the auxiliary sensors 12, 13 are arranged atline-symmetric positions relative to the main sensor 11, so that a phasedifference that is identical to the phase difference θ2 between outputsignals of the main sensor 11 and the auxiliary sensor 12 is producedbetween the output signal 502 of the main sensor 11 and the outputsignal 524 of the auxiliary sensor 13.

FIG. 10 is a diagram for explaining signal production in a case where anoffset is present in output signals of the auxiliary sensors 12, 13. Anexample of a case where an offset offset is present in an output signal533 of the auxiliary sensor 12 at a time of normal rotation of the rotor62 is provided. As described, the threshold voltages thA1, thA2 are setbased on values of the output signal 533 of the auxiliary sensor 12 atthe predetermined timings P1, P2 that are acquired in calibration thatis executed at a time of motor activation. A value of the output signal533 of the auxiliary sensor 12 at the timing P1 that is advanced by 120degrees relative to a rotational angle of the rotor 62 that is 180degrees is set as the threshold voltage thA1 and a value of the outputsignal 533 at the timing P2 at an angle of rotation that is delayed by60 degrees relative thereto is set as the threshold voltage thA2. Thedigital signal 1 that is indicated by a solid line 536 is produceddepending on results of comparison of the output signal 533 of theauxiliary sensor 12 with the threshold voltages thA1, thA2. The digitalsignal 2 that is indicated by a solid line 538 is produced by using adigital signal 535 that is produced from the output signal 502 of themain sensor 11.

In the present embodiment, the threshold voltages thA1, thA2 are setdepending on an offset offset of the auxiliary sensor 12. Similarly, thethreshold voltages thB1, thB2 of the comparator 24 where an outputsignal 534 of the auxiliary sensor 13 is supplied thereto are also setby the output signal 534 that is dependent on an offset of the auxiliarysensor 13. It is possible to set the threshold voltages thA1, thA2,thB1, thB2 of the comparators 23, 24 depending on an offset, so that anoffset cancel part does not have to be provided for the auxiliary sensor12, 13. Therefore, it is possible to simplify a circuit configuration.Additionally, similarly to a case of FIG. 4 , the digital signal 2 maybe produced by measuring a time that corresponds to a phase differenceof 60 degrees relative to the digital signal 1 of the auxiliary sensor12 by also using information of the digital signal 535 of the mainsensor 11, and executing an arithmetic process by using such ameasurement value.

FIG. 11 is a diagram that illustrates a flow of one embodiment ofcalibration. The motor 60 is normally rotated at a constant frequencyforcibly (S10). A driving signal with a predetermined pattern thatnormally rotates the motor 60 at a constant frequency (rotationalfrequency) forcibly is produced in the driving signal production part 35and is supplied to the respective output transistors 41 to 46 of theoutput circuit part 40. Original data of a predetermined pattern arestored in, for example, the memory part 50 and are supplied to thedriving signal production part 35 at a predetermined timing through thesignal processing part 31. Original data may be supplied from an outsideof the driving device 100.

A phase difference between an output signal of the main sensor 11 and anoutput signal of the auxiliary sensor 12 is detected (S11). For example,a phase difference between peak values of output signals of the mainsensor 11 and the auxiliary sensor 12 is detected. A phase differencebetween peak values is detected, so that, for example, it is possible toexclude an influence in a case where an offset is present in an outputsignal of the auxiliary sensor 12.

Whether or not a phase difference is 30 degrees that is a threshold orless is determined (S12). In a case where a phase difference is 30degrees or less (S12: Yes), the auxiliary sensor 12 is selected (S13).That is, the auxiliary sensor 12 that is advanced at a time of normalrotation of the rotor 62 is selected and an output level of an outputsignal of the auxiliary sensor 12 with a phase that is advanced by 120degrees relative to an output signal of the main sensor 11 is detected(S15).

In a case where a phase difference is greater than 30 degrees (S12: No),the auxiliary sensor 13 is selected (S14). That is, the auxiliary sensor13 that follows the main sensor 11 at a time of normal rotation of therotor 62 is selected and an output level of an output signal of theauxiliary sensor 13 with a phase that is delayed by 120 degrees relativeto an output signal of the main sensor 11 is detected (S16).

A result of selection and an output level of an auxiliary sensor at atime of normal rotation of the rotor 60 are stored in a memory of thememory part 50 (S17). A stored detection level is set as a thresholdvoltage of a comparator.

Then, the motor 60 is reversely rotated at a constant frequency forcibly(S18). Control is executed in such a manner that a driving signal with apredetermined pattern that reversely rotates the motor 60 at a constantfrequency (rotational frequency) forcibly is produced in the drivingsignal production part 35 and is supplied to the respective outputtransistors 41 to 46 of the output circuit part 40. Original data thatare provided as a base of a predetermine pattern are stored in thememory part 50 and are supplied to the driving signal production part 35at a predetermined timing through the signal processing part 31. Areason why a step of executing reverse rotation forcibly is provided isto prepare for a case where the motor 60 is reversely rotated.

In a case where the auxiliary sensor 12 is selected at a time of normalrotation of the rotor 60 (S19: Yes), that is, a case where a phasedifference between output signals of the main sensor 11 and theauxiliary sensor 12 is 30 degrees or less, the auxiliary sensor 13 isselected (S20) and an output level of an output signal of the auxiliarysensor 13 with a phase that is advanced by 120 degrees relative to anoutput of the main sensor 11 is detected (S22). Thereby, as explained inFIG. 5 , a detection level (thB2) at the timing P3 before an outputlevel of an output signal of the auxiliary sensor 13 reaches a peakvalue and an output level (thB1) of an output signal at the timing P4before it reaches a bottom value are detected, so that it is possible todetect them as setting values of threshold voltages of the comparator24.

In a case where the auxiliary sensor 12 is not selected at a time ofnormal rotation of the motor 60 (S19: No), the auxiliary sensor 12 isselected (S21) and an output level of an output signal of the auxiliarysensor 12 with a phase that is delayed by 120 degrees relative to anoutput of the main sensor 11 is detected (S23). Thereby, it is possibleto detect a value before an output level of an output signal of theauxiliary sensor 12 reaches a bottom value and a value before it reachesa peak value, as setting values of the threshold voltages thA1, thA2 ofthe comparator 23.

A result of selection and an output level of an auxiliary sensor at atime of reverse rotation of the motor are stored in a memory of thememory part 50 (S24). Stored output levels are set as the thresholdvoltages thA1, thA2, thB1, thB2 of the comparators 23, 24.

For example, calibration is automatically executed at a time of motoractivation, so that threshold voltages of the respective comparators 23,24 are set. Output signal of the respective auxiliary sensors 12, 13 arecompared with respective threshold voltages so as to detect timings whenthe respective threshold voltages are reached, so that it is possible todetect a rotational position of the rotor 62. Additionally, a drivingsignal in calibration at a time of activation may be supplied from anoutside of the driving device 100 to the output circuit part 40.

FIG. 12 is a diagram that illustrates an example of a plane patternwhere the driving device 100 is integrated. In the driving device 100,the main sensor 11, the auxiliary sensors 12, 13, the detection part 20,the control part 30, the output circuit part 40, and the memory part 50are integrally integrated. The auxiliary sensors 12, 13 are formed onboth sides of the main sensor 11. The auxiliary sensors 12, 13 areprovided on both sides of the main sensor 11, so that it is possible toprovide a configuration where a rotational position of the rotor 62 isdetected so as to precede or follow the main sensor 11 depending onrotation of the rotor 62.

In a case where the main sensor 11 and the auxiliary sensors 12, 13 areformed of silicon, for example, it is possible to form it on a singlesilicon substrate integrally together with the detection part 20, thecontrol part 30, the output circuit part 40, and the memory part 50 andintegrally integrate them by a mold resin.

In a case where Hall elements that compose the respective sensors 11,12, 13 are composed of a compound semiconductor, it is possible tointegrate separate chips (non-illustrated) where Hall elements that arecomposed of a compound semiconductor are formed, with a siliconsubstrate where other circuit parts are formed, by a multichipconfiguration, and integrally integrate them by, for example, a moldresin. Furthermore, a part of components may be composed of otherintegrated circuits as external ones. For example, the outputtransistors 41 to 46 that compose the output circuit part 40 arecomposed of high-voltage Double Diffused MOS (DMOS) transistors and areinvolved with heat generation, so that they may be configured as anexternal integrated circuit device.

FIG. 13 is an exploded perspective view of one embodiment of a motorthat incorporates the driving device 100. The driving device 100 ismounted on a support base 200. An exciting coil (non-illustrated) isprovided on a stator 202 and an exciting current is supplied theretothrough the output lines 301 to 303.

The rotor 62 that is composed of a permanent magnet, the stator 202, andthe support base 200 are housed by an upper housing 201 and a lowerhousing 203.

A configuration where the driving device 100 is provided in such amanner that the main sensor 11 and the auxiliary sensors 12, 13 areintegrally integrated is provided, so that it is possible to eliminate aright side part 200A of the support base 200 as indicated by a dottedline. Thereby, it is possible to reduce a cost of a motor. For example,it is possible to divide a flat plate with a ring shape(non-illustrated) into halves so as to provide semi-ring shapes, use oneof them as the support base 200, and use the other as a support base ofanother motor. The driving device 100 where the main sensor 11 and theauxiliary sensors 12, 13 are integrally integrated is provided, so thatit is possible to reduce a cost of a motor.

Although a case where the rotor 62 is of two poles has been explained inan embodiment as described, it is possible to detect a rotationalposition of the rotor 62 by similarly using the driving device 100 evenin a case where the rotor 62 is of four poles, eight poles, or the like.

Although some embodiments of the present invention have been explained,these embodiments are presented as examples and do not intend to limitthe scope of the invention. These novel embodiments are capable of beingimplemented in various other modes and it is possible to execute avariety of omissions, substitutions, and modifications without departingfrom the spirit of the invention. These embodiments and/or variationsthereof are included in the scope and/or spirit of the invention and areincluded in the scope of the invention as recited in what is claimed andequivalents thereof.

What is claimed is:
 1. A brushless motor driving device comprising: anoutput part that supplies an excitation current to an excitation coilthat generates a magnetic field that rotates a rotor; a positiondetection part including a first detection element, a second detectionelement, and a third detection element, each being disposed to face therotor, the position detection part detecting a rotational position ofthe rotor on the basis of output signals from the first to thirddetection elements, the output signals being output in response toapproaching part of the rotor having a specific magnetic pole; and adriving control part that produces a driving signal based on a detectionsignal from the position detection part and supplies the driving signalto the output part, wherein the first to third detection elements andthe driving control part are integrally provided on a surface of asubstrate, the second detection element is provided at a position wherethe second detection element outputs the output signal preceding theoutput signal from the first detection element, and the third detectionelement is provided at a position where the third detection elementoutputs the output signal following the output signal from the firstdetection element.
 2. The brushless motor driving device according toclaim 1, wherein the first detection element is provided at a positionwhere a first center line passing through a center of the firstdetection element passes through a center of the rotor, and the seconddetection element and the third detection element are provided atline-symmetric positions relative to the first center line.
 3. Thebrushless motor driving device according to claim 2, wherein the seconddetection element and the third detection element are provided atpositions where a first angle and a second angle with respect to thefirst center line are equal to one another, the first angle is an anglebetween the first center line and a second center line, the secondcenter line passing through a center of the second detection element andthe center of the rotor, and the second angle is an angle between thefirst center line and a third center line, the third center line passingthrough a center of the third detection element and the center of therotor.
 4. The brushless motor driving device according to claim 1,wherein the driving control part, at a time of normal rotation of therotor, produces the driving signal by using a detection signal of thefirst detection element and a detection signal of the second detectionelement in a case where a phase difference between the detection signalof the first detection element and the detection signal of the seconddetection element is a predetermined threshold or less, or produces thedriving signal by using a detection signal of the first detectionelement and a detection signal of the third detection element in a casewhere a phase difference between the detection signal of the firstdetection element and the detection signal of the second detectionelement is greater than the predetermined threshold.
 5. The brushlessmotor driving device according to claim 4, wherein the predeterminedthreshold is 30 degrees.
 6. The brushless motor driving device accordingto claim 4, wherein the driving control part produces the driving signalby using the detection signal of the first detection element and thedetection signal of the third detection element at a time of reverserotation of the rotor, in a case where the driving signal is produced byusing the detection signal of the first detection element and thedetection signal of the second detection element at a time of normalrotation of the rotor.
 7. The brushless motor driving device accordingto claim 1, further comprising a threshold voltage production part thatsets detection levels for a detection signal of the second detectionelement and a detection signal of the third detection element.
 8. Thebrushless motor driving device according to claim 7, further comprising:a first comparator that compares a level of a detection signal of thesecond detection element and the detection level that is set by thethreshold voltage production part for the detection signal of the seconddetection element; and a second comparator that compares a level of adetection signal of the third detection element and the detection levelthat is set by the threshold voltage production part for the detectionsignal of the third detection element.
 9. The brushless motor drivingdevice according to claim 1, further comprising a memory part that holdsvalues of detection signals of the second and third detection elementsthat are obtained in calibration where the rotor is rotated under apreliminarily set condition.
 10. The brushless motor driving deviceaccording to claim 1, further comprising an offset cancel part that isprovided on the first detection element, wherein the first to thirddetection elements and the driving control part are integrated by a moldresin.
 11. A brushless motor comprising: a rotor; a brushless drivingdevice including an output part that supplies an excitation current toan excitation coil that generates a magnetic field that rotates therotor, a position detection part including a first detection element, asecond detection element, and a third detection element, each beingdisposed to face the rotor, the position detection part detecting arotational position of the rotor on the basis of output signals from thefirst to third detection elements, the output signals being output inresponse to approaching part of the rotor having a specific magneticpole, and a driving control part that produces a driving signal based ona detection signal from the position detection part and supplies thedriving signal to the output part; and a support base that supports thebrushless driving device, wherein the first to third detection elementsand the driving control part are integrally provided on a surface of asubstrate, the second detection element is provided at a position wherethe second detection element outputs the output signal preceding theoutput signal from the first detection element, and the third detectionelement is provided at a position where the third detection elementoutputs the output signal following the output signal from the firstdetection element.
 12. The brushless motor according to claim 11,wherein the first detection element is provided at a position where afirst center line passing through a center of the first detectionelement passes through a center of the rotor, and the second detectionelement and the third detection element are provided at line-symmetricpositions relative to the first center line.
 13. The brushless motoraccording to claim 12, wherein the second detection element and thethird detection element are provided at positions where a first angleand a second angle with respect to the first center line are equal toone another, the first angle is an angle between the first center lineand a second center line, the second center line passing through acenter of the second detection element and the center of the rotor, andthe second angle is an angle between the first center line and a thirdcenter line, the third center line passing through a center of the thirddetection element and the center of the rotor.
 14. The brushless motoraccording to claim 11, wherein the support base is composed of a flatplate with a semi-ring shape.
 15. The brushless motor according to claim11, further comprising an offset cancel part that is provided on thefirst detection element.